<!DOCTYPE html>
<link rel="help" href="https://bugs.chromium.org/p/chromium/issues/detail?id=1498297">
<style>
* {
  margin-top: 100px;
  padding-left: 100px;
  position: sticky;
  bottom: 0px;
}
</style>
<select id="select1" multiple="multiple" style="writing-mode: vertical-rl">
  <optgroup id="optgroup">text</optgroup>
</select>
<select id="select2" >text</select>
<script>
document.body.offsetTop;
select2.add(optgroup);
document.body.offsetTop;
select1.length = 1;
</script>
